Pulse generating system



May 5, 1953 P. E. Fox

PULSE GENERATING sys'rsu 5 Sheets-Sheet 1 Filed Jan. 18, 1949 WQDQ ESQ 3 Sheets-Sheet 2 was P. E. FOX

PULSE GENERATING SYSTEM INVENTOR PHILIP E. FOX

.ATTORNEY WGQUQ QRET May 5, 1953 Filed Jan. 18, 1949 May 5, 1953 P. E. FOX

PULSE GENERATING SYSTEM 3 Sheets-Sheet 3 Filed Jan. 18 1949 INVENTOR PHILIP E. FOX

QHQE mm Sim m ATTO R N EY plate of one of the two tubes constituting the free-running multivibrator I5. The voltage dividing means comprises a resistor |8 (240,000 ohms) shunted by a capacitor I9 (50 micromicrofarads) and a second resistor 20 (220,000 ohms) which is connected between the control grid of the tube and a source 98 of bias potential, here shown to have a voltage of 100 volts. The suppressor grid of tube I1 is connected to its cathode so that the control grid exercises complete control over the flow of current within the tube.

The following description Will relate sometimes to positive, or mark, impulses and negative, or space, pulses. Pulses will be defined according to the direction of the voltage excursion at the plate of a tube at the time the pulse is produced. For example, should the voltage at the plate of a tube change from a low value to a value which is higher and then after a period of time change back to a low value, a positive, or mark, pulse would be produced. The converse would be true for the production of a negative, or space, pulse.

Hence, according to the above definition of pulses, the value of resistors l8 and 20 are chosen such that tube I! will operate as an on-off device, being turned on by positive pulses andbeing turned off by negative pulses generated at the plate of one of the tubes comprising the freerunning multivibrator.

Tube l1 operates as a slicing amplifier. A slicing amplifier is one which is adapted to accept a median part of a voltage alternation. It is well known that the voltage output of a multivibrator is not a rectangularly shaped wave having vertical sides and 90 degree corners. Therefore, if only a part of such a multivibrator produced wave, such as a slice through the middle, is accepted for amplification then a more nearly perfect rectangular wave may be produced from the slicing amplifier because a median slice taken from the multivibrator produced waves will have more or less vertical sides and the cut-off and saturation characteristics of the tube type used will contribute toward the production of approximately square cornered waves.

The mark and space pulses derived from the free-running multivibrator |5 are of such a magnitude that a very considerable over-driving of the control grid of the slicing amplifier tube is obtained. The overdriving may be considered to be both positive and negative with respect to the normally used grid operating voltages. If the slicing amplifier tube-be of the 6SJ 7 type, a grid potential of approximately minus 10 volts will achieve cut-off of substantially all anode current. In this application, the grid is griven to a nega tive potential of approximately minus 28 volts during space pulses and to a positive potential of approximately plus 12 volts during mark pulses. As has been hereinabove explained, this means that a median slice of the multivibrator produced wave will be accepted for transmission through tube |'I. Approximately square corners will be produced by tube I! because that portion of the wave represented by plus 12 volts will be clipped or limited by the fiow of grid current. The lower 18 volts below approximately minus 10 volts, being more negative than the grid cut-off voltage will likewise have little or no effect upon the resultant output wave. The squareness of the wave corners produced will, of course, be dependent upon th individual tube type and other circuit component values used and will not be absolute degree corners, although they will be substantially square.

The amplifier tubes in the present invention are operated according to the above outlined on and off grid overdriving principles.

The output of the tube I1 is transmitted through a voltage dividing means comprising a resistor 2|, shunted by a condenser 22, and a resistor 23 to the control grids of two tubes 24 and 25, said control grids being connected in parallel by a wire 26 and each having series connected parasitic suppression resistors 21 and 28 (each 5,000 ohms). Tubes 24 and 25 serve to effect further shaping of the multivibrator produced wave into an essentially rectangular form and to invert the phase of the waves. Components 2|, 22, and 23 have the same quantitative values respectively as components |8, l9, and 20.

The plate of tube 24 is connected over a wire 21 to a pulse differentiating network shown enclosed by a box 28. The plate of tub 25 is connected through voltage dividing coupling means comprising a resistor 94 of 510,000 ohms shunted by a ccndenser of 50 micro-microfarads capacity, and a resistor 96 of 470,000 ohms to the grid of tube 29, which tube serves mainly as a pulse phase reversing means. The values of components 94, 95, and 96 are usually used in th voltage divider coupling means shown in this invention. The plate of tube 29 is connected via terminal 30 to a second pulse differentiating means 3|.

A differentiating circuit as herein used serves to produce narrow impulses of very short time duration from rectangular waves. It will be noticed that the differentiating circuits enclosed by boxes 28 and 3| each contain a condenser, and a pair of resistances, for example, in box 3|, a condenser 32 of 50 micro-microfarads capacity and resistors 33, 34, respectively, 200,000 and 51,000 ohms. For the purpose of illustration, box 3| is provided with a pair of input terminals 30 and 35 and a pair of output terminals 36 and 3'1. A rectangular wave produced by tube 29 will have in a cycle thereof a pair of discontinmties in the form of abrupt changes in voltage. These abrupt changes in voltage impressed upon the differentiating circuit between terminals 30 and 35 are followed by an exponential charging or discharging of condenser 32. The fiow of current through resistances 33 and 34 during the charging or discharging time produces pulses of output voltage between the output terminals 36 and 37. The duration of the pulse can be made as short as is desired simply by making 32, 33, and 34 small in value. Because the input voltage is a periodic wave having discontinuities an output pulse is produced by the differentiating circuit at each discontinuity of input voltage.

The narrow pulses of short time duration produced by the two diiferentiating networks 28 and 3| are transmitted respectively to tubes 38 and 39. Because these tubes are both biased beyond the cut-ofi point, application of diiferentiat ng network produced negative going pulses wil1 not render said tubes conductive and these negative pulses are hence eliminated. On the other hand, the amplitude of the differentiating network produced positive going pulses is suificient to render the tubes conductive, producing at the plates thereof amplified inverted and shaped short duration negative goin pulses.

.In summary then, the pulses produced by the prir. ary multivibrator l5, amplified and shaped by tube H are transmitted to two chains of tubes,

one chain comprising tubes: 2:4?- and: 3:3,. the other chain; comprising tubes 25, 219;. and! 39.1. Each chain is provided: with; a. difier'entiating circuit inserted immediately preceding. the: last; named tubes: suchv that the: effi'ect oi: the system; thus. far. is to produce negative going pulses at the: end of) each-:chaim. the pulses; of" the. chain comprising tubes Z tand: as. originating: from: the: positive going-.1 wave edge of at multivibrator half cycle; and the. pulses:v of the chain. comprising tubes-125, 29, and 31S originating from the negative-going wave edgeiof. the. same multiyibraton half cycle.

Th plates of tubes 33 and arere'spectively com-moned with the plates ofv tubes? 40: and M comprising single stability? multiv-ibraton 42 of known type. This: single stability multivibrartor, or one-shot multivibrator. as it isrsometimes termed, is in a stable. or. reset state: whentub'e-sal is conducting andv when tube. 401 at cut ofi. Normally tube. M is conducting because its: control grid is biased considerably above. the cut=of value by its connection viaresist'ors 43 and M, respectively 2,000,000 and 200,000 ohms to a source. of positive potential. Also), the low potential existing at the plate of: tube 4 is applied over resistors l5 and: it, respectively510,000 and. 470,000 ohms, which form a voltage divider be.- tween. said. plate and a source 98= of bias potential', tothe: grid of tube 4'0 to maintain this'grid at. a potential more: negative than the cuteoil' value;

The short duration: pulses transmitted through tube. 33 are'applied to the plate of tube 40; or to the. turn-on terminal of: A2, and act to drive thev single-stability multivibrator from its stable state to the unstable state by the release of a cumulative triggering action torender tube conductive and tube at non-conductive. Immediately tube becomes conductive the potential at the turnon terminal drops-from source potential to a potential determined by the tube and. other circuit parameters; Condenser 4? of 100 micro-microfarads capacity then starts to discharge through resistors 13 (20,000ohms)=, 43; and it and: t rough tube lll' until the voltage at the. grid of. tube H approaches and starts to exceed cut-oil potential in a positive direction whereupon a second triggeringaction is initiated to restore the multivibrator to its stablestate: Condenser il recharges. through resistors 4 3", 44; and 48- and over the grid-cathode path of' tube All When. the single stability multivibrator is in its stablestate.

Continuous oscillation of the multivibrator" is prevented because the bias voltages applied to the control grids are so proportioned with respectftothe value of plate potential that oscillation is inhibited at the conclusion of each cycle of operation.

Resistor 53- is made variable so that thetime constant of condenser ll" and' resistors dfl, 44, and 8 and theimpedance of tube 40; taken in combination, may be varied to selectively produce variable restoring time durations of" the multivibrator. Theeiiect of t'his'isthe production of rectangular. waves having selectively variable Widths.

It has been pointed out hereinabove that the negative going pulses produced in the plate cir cult of. tube 39 occur one half cycle later'in'time than those produced by tube 38 with'respect to the primary source of oscillations. The plate. of tube-Sills connected by a wire 5fl'to. the plate of tube il which tube isrendered conductive when.- ever the single: stability multivibraton, or. sec..-

ondary source ofi'o'scillationa Mi is resting; in; its stable equilibrium state; The: point. of; connection betweenthe: plates offtubes: 33 and 47.13 and the. plate: load. resistor 49 (29103.0?01'11118); thevefnn is; termed. the: tum-on. terminal at the-seconds ary source: 015 oscillations. Because; at circuit parameter of; 42' ismade: variable; allowing for the productiomoi:variablertime dnrationpulses there;-

it. is possibleithatw one usingithe: instant. sys:- tem'. ot pulse; generation could; so: ad 'u'stt resistor 43' that pulses havin time dmatiom longer than: one half; cycle: oi the primaa'yf source of. cs."- cillations would be generated.

It is not desirable to allowthisiconditiomto exist; and accordingly; automatio;means comprisings'therchaizrof tubes 2 2.9.; and: 39s, andi includiing diiiierentiating circuit; 3d; are provided: and connected. tothe secondary source ofv oscillations suchthat the negative. going pulsesi generated by; saidv chain will actito. positively reset the: second? ary sources ofi oscillations irom its unstablerstat'a to its stable. state. should. self-restoring. not have occurred. within one half; cycle of the. primary multivibrator. Therefore; it: will. now hammer:-

, stood that. given. any particular frequency of;

oscillation of the. primary source l5; the se'conde ary pulse=source 42limaybe? adjusted togenerata pulses of the same frequency ofioscillati'on having selectively adjustable time: durations; ranging I from theimin'imum permittedi'by tuberandicircuiti characteristics to" a maximum no: longer thantha time: consumed by one" half cycle. of. source oscillation at the-chosen frequency otose cillation. It will-be understood. that thelbala-nca of 15, that is, the ratio ofv mark to: space innpulses, will have no effect onatheirepetitionrfizequency of 42.

Returning now to the plate circuit of: tube: 245 it will benoticed that. the load resistor 5.1L. on 20,000 ohms therefor. has: a. center tap: tois connected a wire 52: leading to the:- input ters minals a.- and h of a double stability trigger- 53u Trigger 53 may be any suitabletriggen havmg twostable equi'librium states; for examp1e,.. the; one disclosed in an applicatiomfierial: N 0 2.569992; filed December 2'7, 1944; Patent No...2';5;3.6,955.;..by R. L. Palmer et' al; andalsdshowmim Eig; 3l.. A property of double stability triggers: oh the: dis closed type is that with each negativezgoingipulse applied to both input terminals a;andjtitheltrige ger will: reverse its equilibrium status;- Hence; for each negative going. pulse produced. at. the plate of tube-25 trigger 5'3 willcreversei ltSl StEtBi The normal state of equilibrium of trigger: 53: is arbitrarily chosen as that state which the right-hand tubeisconducting. 'llhis is.-'imiicated by the X inscribed in the trigger'box; andbycontnection to other circuit elements, for example; tube 8401 switch 88; later to be describe'dg. Triglger 53 output terminal 0 is connected through voltage dividing meansv to? the controllgrid off a coincidence mixing tube 541. Trigger. 53L output terminal f" is connected'throug-h other: voltage dividing means to the control grid:v 0t. another coincidence mixing tube 55. The suppressor grids of tubes 54 and 55 areconnecteddfiparallel and to the output, or turn-off, terminal on. the secondary source ofQsciIlationsAZthrQugh aivolt's age divider-comprising resistors H32 and l'031re spectively; of 680,000 and 330,000 ohms.

In its normal. state of equilibrium terminal" 0 of.- trigger 53' will be at plate" source potential because. the left-hand tube thereof is not con ducting. Thishigh otential" then. will be applied over. the. said voltage. dividing. means acting. to

overcome the grid bias potential and to condition tube 54 for later operation by placing on its control grid a potential substantially above the cut-off value. Similarly, in the reversed state of equilibrium of trigger 53, terminal I will be at plate source potential to likewise condition tube 55, for later operation, by placing on its control grid a positive potential substantially in excess of the cut-ofi value, Because trigger 53 is reversed in status by each negative pulse produced by tube 25, or by multivibrator 15, it may be stated that tube 54 is conditioned for one multivibrator cycle while tube 55 is conditioned for the next such cycle.

As stated above, the output pulses produced by the single stability multivibrator are applied to the suppressor grids of both tubes 54 and 55. Each reversal of the single stability multivibrator acts to apply sufficient positive potential to overcome the suppressor grid bias voltage and to render one or the other of tubes 54 and 55 conductive depending upon the condition of their control grids. For example, with trigger 53 being in the equilibrium state shown in the drawing, a positive pulse applied from 42 to the suppressor grid of 54 will render this tube conductive to produce therefrom a pulse which will be termed an AP pulse. A pulse produced by tube 55 is termed a BP pulse. Therefore, since trigger 53 is alternated with each negative going pulse produced by the primary source l5, it will be understood that tubes 54 and 55 are alternately conditioned and that these alternately produce pulses AP and BP under the control of the secondary source of oscillations 42.

Amplifying means H and I2 are respectively connected by wires 55 and i passing through terminals 92a and 92b, respectively, to the plates of tubes 54 and 55 for the purpose of amplifying, shaping, and providing outputs of different impedance values for the AP and BP pulses. The circuit arrangement of amplifier H is shown in detail in Fig. 4, while amplifiers l2, l3, and [4 are shown diagrammatically as they all are substantially equivalent to amplifier l l. The operation Of amplifier II will be described and it Will be understood that the operation of amplifiers l2, l3, and I4 is similar thereto.

. The plate of tube 54 is connected through the usual voltage dividing means to the grid of a tetrode tube 58 by wire 56. Tube 58 acts as an amplifier and phase reversing device. Tube 58 is a 25L6 beam power amplifier tube and its plate is connected over three separate wires 59, 6!, and 63, respectively, to a coincidence mixing tube 60; through a voltage dividing means to another power amplifier tube 62; and to a coupling capacitor 64. Tube 62 is another beam power amplifier which has large power handling capabilities. The plate circuit thereof is provided with a tapped load impedance 65, the tap being connected to an output terminal 86 to which may be connected other devices requiring negative going impulses and which do not form a part of this invention. Coupling capacitor 64 is connected to a diode direct current restoring means 51 and to the control grid of a second power amplifier tube 68 similar to tube 62 in power handling capabilities. Tube 58 is connected as a cathode follower type of amplifier having an output terminal 69 connected to the cathode thereof. This type of amplifier is well known in the art and no explanation of the principles thereof need be given. The grid bias is supplied to tube 68 by resistors 99, I55, and IQI, in combination. Resistor Ill-i has a D. C. restorer or diode clamper 61 connected in parallel therewith operating according to known principles of operation such as may be found in a volume, Principles of Radar, by the Stafi of the Radar School, Massachusetts Institute of Technology, Second Edition.

It has been above said that amplifier l2, connected by wire 51 to BP pulse tube 55 is equivalent to amplifier ll. Wire 10 connected thereto corresponds to wire 59a of amplifier H with the exception of being connected to a source of supply pulses of negative polarity instead of positive polarity impulses.

Amplifiers l3 and [4 are likewise equivalent to amplifier II. Amplifier I4 however, does not have any output wire corresponding to wire 59a of amplifier II. Also, as shown by the drawing, amplifiers l3 and I4 are provided each with only a single output terminal corresponding in impedance value to output terminal 69 of amplifier ll. Hence, the power amplifying tube corresponding to tube 62 of amplifier H is not present in amplifiers l3 and I4. The circuit arrangements of amplifiers ll, l2, [3, or [4 are not part of the instant invention and are described solely for the sake of completeness. Refer now to Figs. 1 and 2.

It was stated hereinabove that wire 59a is adapted to supply positive going AP pulses from amplifier II to the suppressor grid of a coincidence mixing tube 60 through the usual voltage dividing means. The control grid of tube 60 is connected, also through an appropriate voltage divider, to the f terminal of a double stability trigger H. Terminals a and h of said trigger are connected by wire 10 to a source of negative going BP pulses acting to operate said trigger from one of its stable states to the other for each negative BP pulse received. The d terminal of trigger H is connected by wire 12 to the input a and h terminals of another double stability trigger 73. The normal stable states of triggers TI and 13 are indicated by an X placed at the appropriate side thereof.

Since trigger H is alternated from one stable state to the other by each negative BP pulse, it will be appreciated that for every two such pulses this trigger will produce a negative pulse on its terminal 11 which is connected to trigger is terminals a and h thereby operating trigger 13 from one stable state to its other stable state. In other words, triggers H and I3 constitute a frequency dividing chain adapted to divide the frequency of occurrence of supplied BP pulses by 2 in the case of trigger 7|, and by 4 in the case of trigger I3.

Because the control grid of coincidence mixing tube 60 is connected to output terminal 1 of trigger H said grid will operatively condition tube 60 for every odd numbered BP pulse. It will be recalled that the suppressor grid of said tube is conditioned by AP pulses and that a degree phase difference exists between AP and BP pulses. Hence, tube 60 will be rendered conductive during the time of occurrence of every second AP pulse. The pulses produced by the coincidence mixing tube 60 will occur at half frequency, with respect to AP pulses, and are termed CP pulses. CP pulses are transmitted over a wire 14 from the plate of tube 60 to amplifier I3 wherein they are adequately amplified before being supplied to an output terminal 690.

Terminal f of trigger 13 is connected to the control grid of another coincidence mixer 15 through the usual voltage dividing means. Since trigger 13 is alternated from one stable state to and Run. 'One inectedto a sourceof positive potential, the-other terminal of switch T! being connected through a-resistor to one grid f a double stability trigger 19; the other terminal o f'switch 1-8 also is con- :nected through a resistor to "the other grid of said trigger. Operation of either switch imposes "high potential on the respectively connected grid other of its stable states.

'the other :by every second '13? purse, it will 'be appreciated :that "mixer *1 5 is operatively conditioned for operation 'prior to :the o'ccurrence of every fourth A-P pulse. .Awire "59b supplies positive going CP pulses from amplifier is through the usual voltage divider to the suppressor grid .01 mixer 15. Hence, "mixer rendered conductiveduring the times'of socol; nee every :secondEP pulse. Thepulses"producedby m 2 tube IS are termed EPipulses are transmitted over a wire 16 to amplifier I t, herembeiore ole-- scribed, which serves to amplify said pulses for use by outside devices.

"The desired sequence of pulses *from'the various outputs 66a and 69a, 66b and .6311, 358e, 69d of the system is respectively pulses :and BP pulses at fundamental frequency. "GP pulses "at fundamental frequency and EP pulses at "fundamental frequency, that iorder see iorzexample, 5.

To secure such a sequence of pulses, switch controlled d scharge means are employed to reset triggers .53, H, and '13 to their "stablestate shown. Also, it is essential that the -primary source oscillator start with a positive going pulse 'for'the reason that trigger 53 must remain in this state in :order that the first pulse produced by the secondary source of oscillations underthe -control 0f the primary :source ofoscillations be effective upon mixer 54 to produce therefrom an AP pulse.

The 'pulse generating system is provided with a .zpair of switches ll and 18, respectively Stop terminal of each switch is confor effecting reversal of the trig er to one or the "In Fig. 1, switch '1? is shown closed thereby-maintaining trigger 1 9 "conductive in its left-hand tube. Operation of switch '58, which ismechanically interconnected with switch Tl acts to -open switch Tl and close switch 18 to place irom'left-h'and conduction to right-hand conduction. The 0 terminal of trigger E9 is connected over the usual voltage dividing means to' the con- :trol of tube 80.

Whentrigger F19 "rests in the normal stable'state switch 'l'l closed, the potential at trigger "terminal 0 is :tiepressed and tube -80 is :not conducting. *When switch :l'fl is controlling :the -.trigger :the potential at terminal 0 is equal to :that :of the source of potential and tubeall is rendered conductive.

"The grid of a itriode tubes! is connected throughrthe usual voltage dividing means to the plate :of tube '30. 'When tube 8'!) is conducting plate current the potential "at the plate thereof is depressed which potential acts in combination .lilith the Voltage divider, and "bias potential source :to impress 'a bias potential upon the-grid of tube 8! substantially more negative than the cut on" "value. On the other hand, when tube 8.0 is non-conductive, atube 8| is rendered con-- ductive. The plate of tube T8,! is parallel connectedwith the plate of one of the tubes comprising .the primary free running m-ultivihrator 15,, .said plate :being the pulseoutput terminal thereof. .The pulse output tube .plate .of multivihrator .I5 and .the pLate of tube .8] thus have a positive potential upon the. right-hand grid :of the trigger reversing same :common load-resistor 82. 'Whenever'tube 8:! is rendered conductive, current flow through reesistor 82 reduces the potential existing at the said pulse output terminal "to such a value that the amplitude of the oscillations produced by 'multivibrator are insufiicient to effectively excite the :grid of slicing amplifier tube ll. Hence, for i all eiiective purposes imultivibrator ('5 can be said to be turned off whenever switch 77 is closed. The instant tube :81 'is rendered none-conductive by the :means hereinabove set forth, the potential existing at :the said pulse output terminal will make a positive excursion to :start the system output pulse sequence with .an :AP :pulse.

with respect to the cancelling of triggers 153, H, and 3 to their normal states shown, fboth switchable means and electron discharge :means are shown.

Because ofthe requirements of apparatus connectible to the pulse genera-ting system, said lapparatus forming no 'partof the present-invention, it is preferred that switchable means, first :named, he used to normalize triggers 53,11, and 1 .3. However, in other cases of use it is convenient'to be :able to start and stop the system "by using only a single switch (such @as switch ll-l8) and accordingly a "trigger normalizing :means comprising a pair of .tubes '83 and 84 is shown as a modification.

Changeover between the two 'modes of trigger cancellation is efiectuated by means of a group of connections shown dotted son the diagrams. The connections labelled 35a and 85b relate to the usually used switchable means, while the connections labelled :Sfid, filth, and 86c relate '"to the modification means.

Referring to Fig. 3- and to triggers 53, ll, and "in Fig. 2, it is "to 'be noted that wire '81:con- :necting terminal cc with a -10!) vysource of bias potential is to be disconnected. With connections 85a, 85b made, Fig. 2, and the 86a, "36b, and Bfic connections disabled, terminals cc on all triggers =53, N and 13 are connected to one terminal of a normally closed push-operated switch 83. The other terminal of said switch is-connected through -a--res'istor on to a source of biasing potential. Assume for the moment that 'multiv ibrator "t5 is stopped at time-t shown by a vertical line 89 in Fig. 5. At this time, triggers VI, and '13 are all in their stable state'other than the normal state. Operation of switch *88 breaks the connection between terminals cc; leading through resistors Bil-and individual trigger resistors '6 or as 'thecase maybe, to the v selected grids and the source of-biasing potential.

In effect-bias voltage is totally removed; permitting the grid to lose control of tube conduction; such action initiates 'a cumulative-triggering operation to render the selected trigger tube canductive and thereby reset the triggers to their shown normal stable state.

New "treating the modification means; connec- 'tions and 35b are disabled "and connections illn. 55b, and 860 made. "Hereinahove it was explained that whenever switch ll was ;closed,tube 23-5 "would be rendered non-conductive and that tube 8i would lac-rendered conductive. The control grid of tube 83 is alsoconnected to the plate of tube to, and similar to tube 8! is controlled lay the tubetll such that when 'isnon-conductive, tube 8'3 is rendered conductive. The plate oftuhe 83 is capacitively .coupled to 'the'grid of tube Bil, said grid also having a resistive connection El .01 15.10.;000 ohms .to ground potential. The cathode of tube .84 is connected directly to .a

'tarily render now to both Figs. 2 and 3. is connected to all trigger terminals cc.

minu 100 volt source of potential. The plate of tube 84 is connected, via the removable connec- 11 is closed and run switch I8 is opened. Operation of said switches reverses trigger l9 produc ing therefrom on terminal a negative going pulse. Said pulse, of indefinite duration, renders tube 80 non-conductive, the rise in plate potential thereof being transmitted via connection 860 to the grid of tube 83 to render said tube conductive. The negative change in plate potential, with respect to the plate of tube 83, is transmitted over wire 93 and through capacitor 9| (500 micro-microfarads) to the grid of tube 84, normally conductive, and is effective to momentube 84 non-conductive. Refer Because wire 81 is disconnected in triggers 53. H,

and 13 it becomes evident that the plate load impedance for tube 84 comprises the three resistors, for example in Fig. 3. 8, 5, and 1 series connected in each trigger between terminal cc and the positive 150 volt source and parallel connected between the three triggers. Hence, the positive pulse produced by making tube 84 become momentarily non-conductive is applied to the respective trigger grids rendering the affected'trigger tubes conductive and reversing the said trig ers to their shown normal state.

While there have been shown and described and pointed out the fundamental novel features of the invention has applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. An electrical impulse producing system having a plurality of output terminals, a source of impulses occurring at a fundamental repetition frequency, impulse counting means comprising a cascade connected chain of triggers which is responsive to said source of impulses and acting to count a succession of impulses relative to said source of impulses, and coincidence mixing means adapted to be controlled by impulses arising from said source and said counting means for the production of impulses of predetermined equal widths and of different repetition frequencies at each of said plurality of output terminals.

2. In a system of the character described, in combination, primary source means for generating electrical waves of substantially square shape, secondary means driven by said primary source means for generating electrical waves of selectable mark and space relation, pulse shaping means coupling said primary source means and said secondary means and responsive to the primary source means for operating the secondary means throu h a secondary wave cycle, a pair of output terminals, and a pair of mixing means each operatively controlled by said primary source means for transmitting successive impulses generated by said secondary means alternately to said output terminals.

3. In a system of the character described, in combination, selectively variable frequency primary source means for generating electrical The plate of tube 84 waves of unequal mark and space relationship, secondary means driven by said primary source means for generating electrical waves of adjustable mark and space relation at a freouency determined by said primary source means, pulse shaping means coupling said primary source means and said secondary means for initiating the operation of the secondary means through a secondary wave cycle, other pulse shaping means responsive to said primary source means acting to limit the maximum time duration of the mark impulse generated by said secondary means, a pair of output terminals, and a pair of coincidence mixing means each of which is responsive to alternate wave cycles generated by said primary source means for transmitting successive impulses generated by said secondary means alternately to said output terminals.

4. An electrical impulse producing system comprising, primary oscillation means of the multivibrator tvpe for generating electrical waves of substantially rectangular shape, secondary oscillation means comprising a single stability multivibrator, pulse shaping means responsive to said primary oscillation means in each wave cycle thereof for operating the secondary oscillation means through a secondary wave cycle, a double stability trigger which is operable to different ones of either of two sustained electrical on and off states and responsive to successive wave cycles generated by said primary oscillator means to shift its state once for each primary wave cycle, and a pair of electron discharge tubes each of which has first and second grids for exercising control over the electron stream therein, said first grids being connected to said double stability trigger for deriving control potentials therefrom and said second grids being parallel connected to said secondary oscillation means for deriving a control potential therefrom whereby said pair of electron discharge tubes are alternately responsive to successive wave cycles generated by said primary oscillation means for transmitting successive impulses generated by said secondary oscillation means.

5. An electrical impulse producing system comprising a multivibrator for generating electrical waves of substantially square shape, a first trigger which is operable to different ones of either of two sustained electrical on and off states and responsive to successive wave cycles generated by said multivibrator to shift its state once for each Wave cycle thereof, a start and stop switch, a second trigger which is operable to different ones of either of two sustained electrical on and off states responsive respectively to the start and stop positions of said switch, and discharge means for applying signals representative of the on and off states of said second trigger to said multivibrator and to said first trigger to cause the multivibrator and the first trigger to stop and start synchronously in a chosen relationship.

6. An electrical impulse producing system for generating a succession of electrical impulses of predetermined width and predetermined spacing at predetermined repetition frequencies including a source of oscillation, a plurality of output terminals, a cascade connected chain of triggers, each operable to different ones of either of two sustained electrical on and off states and responsive to said source of oscillations, a plurality of coincidence mixers each responsive to a dif ferent trigger in said chain of triggers and to said source of oscillations for transmitting successive impulses from said source of oscillations '13 to said :output :termmals in .-.a predetermined progression.

:7 An electrical impulse producing systemcomprising a :multivibrator x for "the production oi a succession of "electrical impulses occurring at a selectable predetermined vfrequency, "a pulse difierentiating circuit responsive to said succession of electrical impulses for producing sharp short time duration impulses therefrom, a single stability multivibrator having a normally inactive status and an active status from which it *is self-restoring to its inactive status and responsive to the impulses produced by said differentiating circuit, variable resistance means for adjustably timing the duration of .the active status of the single stability 'multivibrator, a double stability trigger which ,is operable to d iffierent ones of either oft-two sustained electrical on and ofil-states and responsive to the succession of electrical:'impulses produced by said multivibrator, -:a s'irst pair ojfcoincidence mixers each havingzfirst and second grids for controlling the respective electron streams therein, said .firstgrids being 011- nected to said double stability trigger for deriving icontrol potentials thereiromand said second grids being parallel connectedsto said single stability multivibrator for deriving a control potential therefrom and alternately responding to the successive impulses generated by said multivibrator at its predetermined repetition frequency for transmitting successive spaced impulses generated by said single stability multivibrator, a pair of pulse shaping amplifiers each respectively responsive to the impulses produced from said first pair of coincidence mixers, a cascade connected chain of double stability triggers responsive to the impulses produced by one of said pair of pulse shaping amplifiers, and a second pair of coincidence mixers each responsive to a different trigger in said chain of triggers, and one of said mixers being responsive to one of said pulse shaping amplifiers, the other mixer being responsive to the output of the last named mixer, whereby a progression of impulses of predetermined widths and spacings at predetermined frequencies are produced from said pair of pulse shaping amplifiers and said last named coincidence mixers 8. An electrical impulse producing system having a plurality of output terminals comprising, in combination, a source of oscillations occurring at a selectable frequency, means comprising a plurality of double stability triggers connected in cascade responsive to said source of oscillations and adapted to generate a plurality of sub-harmonic repetition frequencies, coincidence mixing means responsive to both said source of oscillations and to impulses generated by one of said plurality of double stability triggers, and a plurality of other coincidence mixing means adapted to be connected to said output terminals each of which is responsive to the impulses generated by different ones of said plurality of double stability triggers and to the output impulses produced by a mixer under control of a double stability trigger producing impulses having a repetition frequency of 2 where f is the pulse repetition frequency of impulses produced by any of the plurality of coincidence mixers, whereby a predetermined progression of trains of impulses related one to another by integral phase and frequency ratios are produced at said output terminals.

9. An electrical impulse producing system comprising a multivibrator for generating electrical 1114 waveslof w'substantially squ'are'zshape, a first trigger which is operable to different ones of either oftwo sustaincd electrical on and off states and "responsive to successive wave cycles generated by said multivibrator to shiftits state once for each'wave cycle thereof, a start and stop switch, a second trigger which is operable to difierent ones of either of 'two sustained electrical on and off :states responsive, respectively, to-=the start and stop positions of said switch discharge means for deriving and applying signals representative of the on and bit states of said second trigger to said mu'ltivibrator and to said first trigger to cause "the multivibrator and the first trigger to stop and start synchronously in a chosen relationship, a pulse differentiating circuit responsive to said succession of electrical impulses for producing sharp short time durationjim-prilses therefrom. a single stability amultivibrator having a normally inactive status and an active status from which it is self-restoring to its inactive status and responsive to the impulses produced by said difierentiating circuit, variable resistance means for adj ustably timing theduration of the active status of the single stability-multivibrator, a first pair of coincidence mixers each having first and second grids for controlling the respective electron streams therein, said first grids being connected to said first double stability trigger for deriving control potentials therefrom and said second grids being parallel connected to said single stability multivibrator for deriving a control potential therefrom and alternately responding to the successive .J impulses produced by said multivibrator at its predetermined repetition frequency for alternately transmitting successive spaced impulses generated by said single stability multivibrator, a pair of pulse shaping amplifiers each respectively responsive to the impulses produced from said first pair of coincidence mixers, a cascade connected chain of double stability triggers re sponsive to the impulses produced by one of said pair of pulse shaping amplifiers, and a second pair of coincidence mixers each responsive to a different trigger in said chain of triggers, one of said mixers being also responsive to one of said pulse shaping amplifiers, the other mixer being also responsive to the output of the last named mixer, whereby a progression of impulses of predetermined widths and spacings at predetermined frequencies are produced -from said pair of pulse shaping amplifiers and said last named pair of coincidence mixers.

10. An impulse producing system comprising, in combination, a variable frequency multivibrator adapted to generate electrical waves of approximately equal mark to space ratio at a fundamental repetition frequency, a single stability multivibrator adapted to generate electrical waves of variable marl; to space ratio and responsive to said waves of equal mark to space ratio, a double stability trigger which is operable to diiierent ones of either of two sustained electrical on and off states and responsive to said Waves of equal mark to space ratio for producing impulses at a submultiple repetition frequency, and a pair of coincidence multi-gfld mixers adapted to respond to the variable marl: to space ratio waves of fundamental repetition frequency produced by said single stability multivibrator and to impulses of sub-multiple repetition frequency produced by said double stability trigger for the production of two trains of pulses alternately occurring at said fundamental repetition frequency.

11. An impulse producing system comprising, in combination, a variable frequency multivibrator adapted to generate electrical waves of approximately equal mark to space ratio at a fundamental repetition frequency, a single stability multivibrator having a normally inactive status and an active status from which it is self-restoring to its inactive status and adapted to generate electrical waves of variable mark to space ratio responsive to said waves of equal mark to space ratio, a first double stability trigger which is operable to different ones of either of two sustained electrical on and off states and responsive to said waves of equal mark to space ratio for producing pulses at a sub-multiple repetition frequency, a pair of coincidence multi-grid mixers responsive to the variable mark to space ratio waves of fundamental repetition frequency and to the sub-multiple repetition frequency impulses for the production of two trains of impulses alternately occurring at said fundamental repetition frequency, a start and stop switch, a second double stability trigger which is operable to different ones of either of two sustained electrical on and off states responsive, respectively, to

the start and stop positions of said switch, electron tube discharge means for deriving and ap plying signals representative of the on and ofi states of said second trigger to said multivibra tor and to said first trigger to cause the multivibrator, the first trigger and the pair of coincidence mixers to be started and stopped synchronously in a chosen relationship for the pro-'- duction of a predetermined progression of'the alternately occurring two trains of impulses occurring at said fundamental repetition frequency from said pair of coincidence mixers.

PHILIP E. FOX.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,132,654 Smith Oct. 11, 1938 2,145,332 Bedford Jan. 31, 1939 2,217,957 Lewis Oct. 15, 1940 2,271,186 Finch Jan. 27, 1942 2,392,114 Bartelink Jan. 1, 1946 2,413,182 Hollingsworth et a1. Dec. 24, 1946 2,418,521 Morton et a1 Apr. 8, 1947 2,561,172 Bischoff July 17, 1951 

